The two have what sounds to be a rather spirited history of collaboration. Willems, who began his career (and won six Emmys) as a writer and animator forSesame Street, worked with Warburton on two Cartoon Network shows that aired between 2000 and 2006. “I was Tom’s boss, then he was mine, and we were terrible to each other while we were on top,” Willems says. “First he was a director on my show,Sheep in the Big City, and then that was canceled to make room for his show,Codename: Kids Next Door. So he said, ‘Now that you’re no longer my boss, and I know how awful you were as that, I want to hire you as my head writer.’ So I became that.”